1. Field of the Invention
The present invention relates to an engine control apparatus for a vehicle, and more particularly relates in particular to an engine control apparatus for stopping the engine and cutting a fuel supply to a vehicle equipped with an automatic transmission.
This application is based on Japanese Patent Application No. Hei 11-219360, the contents of which are incorporated herein by reference.
2. Description of the Related Art
Conventionally, hybrid vehicles are well-known that carry a separate motor in addition to a drive engine as a power source. Hybrid vehicles are divided into a series hybrid vehicle in which the engine drives a generator that outputs electric power to operate the motor to drive the wheels, and a parallel hybrid vehicle in which a motor connected to the engine is used to assist the rotation of the drive shaft of the engine as well as to charge of electrical energy to an electricity storage apparatus using the same motor or a separate generator.
Such hybrid vehicles are advantageous compared with the vehicles equipped with conventional engines because they enable to operate the engine in a range of roughly constant rotational speed where fuel consumption and exhaust emissions are low, or they are able to reduce operating load on the engine.
Also, in some of the hybrid vehicles, the operation of the engine may be stopped under certain operating conditions as disclosed in a Japanese Unexamined Patent Application, First Publication, Hei 8-317505.
In such a hybrid vehicle capable of stopping the engine under certain operating conditions, there are advantages because overcharging of the battery can be avoided or fuel consumption is further lowered by stopping the engine; however, this technology can sometimes lead to the following problems.
That is, if the engine is stopped while the automatic transmission, including the continuously variable transmission (CVT), is not in a ready-to-move condition, the automatic transmission, which is operated by the oil pressure generated by power output by the engine, is unable to function when the engine is stopped. When the vehicle is to start moving again, because the transmission is engaged in a reduction ratio that existed when engine-stop was executed, acceleration is slow and the time interval required for the starting clutch to fully engage is increased so that the fuel consumption is increased.
Also, when the vehicle is ready to move, there are problems such that oil pressure required to return to a move-enabling reduction ratio is robbed, resulting in inadequate lubrication of the starting clutch or slipping of the drive belt as a result of insufficient lateral pressure on the pulley.
It is therefore an object of the present invention to provide an apparatus for controlling an engine for a vehicle so that the apparatus provides a waiting period so that the engine is ready to start moving before the engine is stopped.
The first aspect of the present invention, an engine control apparatus for a vehicle, having a continuously variable transmission (CVT 3, for example), coupled to an engine (engine 1, for example) which generates a drive force, for driving wheels (drive wheel W, for example), so that, when the vehicle is in a stop-event, to enable stopping or restarting of operation of the engine in response to specific driving conditions, comprising: a fuel supply cut device (step S320, for example) for stopping operation of the engine while continuing to cut supply of fuel to the engine, when the vehicle is in a deceleration event; a vehicle velocity detector (vehicle velocity sensor 4S, for example) for detecting a traveling velocity of the vehicle; and a deceleration detector (a device for computing acceleration based on the change in output data from the vehicle velocity sensor 4S) for detecting deceleration of the vehicle, wherein the fuel supply cut device reverts from a fuel supply cut condition when the traveling velocity of the vehicle detected by the vehicle velocity detector is lower than a predetermined velocity and a deceleration detected by the deceleration detector is higher than a predetermined deceleration (according to determinations in steps S65 and S66, for example).
According to the first aspect of the present invention, because a vehicle velocity detector and a deceleration detector are provided and the fuel supply cut device is designed to revert from the fuel supply cut condition according to vehicle velocity and deceleration, it is possible to return the reduction ratio of the continuously variable transmission to the restart enabling reduction ratio before engine-stop is executed.
The second aspect of the present invention, an engine control apparatus for a vehicle, having a continuously variable transmission (CVT 3, for example), coupled to an engine (engine 1, for example) which generates a drive force, for driving wheels (drive wheel W, for example), so that, when the vehicle is in a stop-event, to enable stopping or restarting of operation of the engine in response to specific driving conditions, comprising: a fuel supply cut device (step S320, for example) for stopping operation of the engine while continuing to cut supply of fuel to the engine, when the vehicle is in a deceleration event; a vehicle velocity detector (vehicle velocity sensor 4S, for example) for detecting a traveling velocity of the vehicle; and a reduction ratio detector (a device for computing a ratio of output of engine speed sensor 1S and output of output shaft rotation sensor 3S) for detecting reduction ratio of the continuously variable transmission, wherein the fuel supply cut device reverts from a fuel supply cut condition only during an interval in which a reduction ratio detected by the reduction ratio detector is lower than a reduction ratio predetermined in accordance with a traveling velocity detected by the vehicle velocity detector (according to determinations in steps S67 and S68, for example).
According to the second aspect of the present invention, because a vehicle velocity detector and a reduction ratio detector are provided and the fuel supply cut device is designed to revert from the fuel supply cut condition according to vehicle velocity and reduction ratio, it is possible to return the reduction ratio of the continuously variable transmission to the restart enabling reduction ratio before engine-stop is executed.